This invention relates to scrubbers for removing hydrocarbons and particulate matter from exhaust gases.
When an open flame is used in conjunction with an industrial process, antipollution laws require that the resulting gases be cleaned of any unburned hydrocarbons and particulate matter resulting from the combustion process before the gas is exhausted to the atmosphere. A typical application of this type is in the lumber industry where large natural gas fired veneer dryers are used in the production of plywood. Large volumes of heated air are used to dry sheets of veneer after they have been cut and as a result the exhaust gases from the dryers contain the undesirable exhaust products of the flame combustion as well as undesirable materials driven off from the veneer in the drying process.
In the past, numerous attempts have been made to provide scrubbers for removing these materials from the exhaust gases emitted from equipment such as veneer dryers, however, none have proven entirely satisfactory. In addition to being extremely efficient in the removal of undesirable materials from the exhaust gas, the dryers must be capable of handling large quantities of gas while operating on a nearly continuous basis. One prior art approach is to fashion a scrubber around large volume settling chambers so that the exhaust gases are greatly decelerated in order that the undesirable materials are precipitated out. However, since such large volumes of exhaust gas are being produced, to be effective, such chambers have to be so massive as to present serious siting problems in most applications.
Another approach is to pass the air through filters of progressingly smaller filtering capacity to mechanically remove the undesirable materials from the exhaust gases. However, due to the large volume of gas being cleaned, massive filters are required which are, by their very nature, expensive. In addition, unless great care is taken, filters tend to cause excessive back pressure which effects the operaion of the dryers. Also filters must be periodically cleaned which results in periods of downtime for the dryer thereby increasing its cost of operation.
Combinations of settling chambers and filters, along with more exotic filtration means, are often used to create hybrid scrubbers which are reasonably efficient in their stated objective. However, such scrubbers are quite complex and accordingly expensive to fabricate, thereby increasing the cost of the process.
The scrubber of the present invention overcomes the aformentioned shortcomings and disadvantages of the prior art scrubbers by providing a series of rectangularly cross-sectioned substantially enclosed chambers which are interconnected to each other end-to-end along an axis of flow which is perpendicular to their cross sectional area. Located between each adjacent pair of chambers is a common baffle wall having the same cross sectional area as the chambers.
Elongate baffle tubes which pass through each of the baffle walls in order to connect the adjoining chambers to one another, have cross-sectional areas which are much less than the cross-sectional areas of the chambers. The baffle tubes contain series of baffle plates which extend completely between opposed sides of the baffle tubes but extend only partially between their top and bottom surfaces. The baffle plates are alternately joined to the tops and bottoms of the baffle tubes so as to form circuitous paths therethrough. In addition the baffle tubes are staggered in the vertical direction in alternate baffle wall so that the flow of the gas through the entire scrubber is also circuitous. Spray nozzles located within each of the chambers and adjacent to each of the baffle plates in the baffle tubes spray water into the scrubber in order to dampen the gases and to wash the baffle walls and baffle plates to remove hydrocarbons and particulate matter which have become collected on them.
Drain means associated with each of the chambers collects the water from the spray nozzels and transfers it to recycling means which removes the hydrocarbons and particulate matter from the collected water so that the water can be reused. Inlets and outlets are located in the respective end chambers for passing the exhaust gases into and out of the scrubber.
Accordingly, it is a principal object of the present invention to provide a scrubber for removing hydrocarbons and particulate matter from exhaust gases which is simple of operation and inexpensive to fabricate.
It is a further object of the present invention to provide such a scrubber which is capable of handling large flow rate of exhaust gases.
It is a further object of the present invention to provide such a scrubber which operates continuously without the requirement of periodic shutdown for maintenance and cleaning.
The foregoing objectives, features and advantages of the present invention will be more readily understood upon consideration of the following detailed description of the invention taken in conjunction with the accompanying drawings.